Conventional hypodermic needles are optimized for injections and are non-coring needles, typically long pointed steel tubes that are pushed through the skin to provide subcutaneous injections. They are typically used to deliver fluids, medicine, or to take samples of blood or other fluids. Subcutaneous injections into the fat layer between the skin and muscle are typically given at a depth of greater than 3.5 mm. Needles utilized to withdraw blood are typically inserted to a depth of between 7-10 mm below the skin surface. The geometry of such needles attempts to guarantee that the needle will penetrate the body surface by making the tip of the needle pointed, and designing the remainder of the opening of the needle such that “coring” is minimized. Coring is the result achieved when a portion of tissue material through which that needle has penetrated obstructs the lumen of the needle, proximal to the pointed tip. In addition, the geometry of such needles typically aims to reduce the pain and discomfort experienced by patients who are undergoing such procedures. With the purposes and applications for which typical hypodermic needles are used, they are generally adequate.
The implantation of follicular units or hair grafts poses a unique problem, requiring the insertion of a follicular unit or hair graft containing naturally occurring aggregates of 1 to 4 hair follicles, into a body surface at a depth which is typically no greater than 4-5 mm. Usually, in known hair implantation procedures using hand-held tools, incisions for implantation sites may be made by a blade or by a conventional non-coring needle or cannula, and then the previously harvested hair grafts are placed manually by the physician or technician in such sites with the use of forceps. Therefore, to improve the efficiency of the implantation procedure, there is a need for instruments and methodologies that allow for the effective implantation of hair grafts through the needle or cannula without the use of the forceps. Such implantation of follicular units using a needle or cannula presents issues which are not encountered or considered when using a hypodermic needle in a conventional manner, such as for example, requiring that the implanted hair graft and those around it remain implanted when the needle is withdrawn, and additionally imposing that the integrity of the follicular unit or hair graft be maintained, a problem which a typical hypodermic needle does not address.